A boat transition state is also possible, and can lead to side products:

The aromatic Claisen Rearrangement is followed by a rearomatization:

When the ortho-position is substituted, rearomatization cannot take
place. The allyl group must first undergo a
Cope Rearrangement to the para-position
before tautomerization is possible.

All Claisen Rearrangement reactions described to date require temperatures of
> 100 °C if uncatalyzed. The observation that electron withdrawing groups at C-1
of the vinyl moiety exert a positive influence on the reaction rate and the
yield has led to the development of the following variations: